package com.etop.jansing.util;

public class MD5 {
    /**//*
     * 下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的， 这里把它们实现成为static
     * final是表示了只读，切能在同一个进程空间内的多个 Instance间共享
     */


    static final int S11 = 7;
    static final int S12 = 12;
    static final int S13 = 17;
    static final int S14 = 22;
    static final int S21 = 5;
    static final int S22 = 9;
    static final int S23 = 14;
    static final int S24 = 20;
    static final int S31 = 4;
    static final int S32 = 11;
    static final int S33 = 16;
    static final int S34 = 23;
    static final int S41 = 6;

    static final int S42 = 10;

    static final int S43 = 15;
    static final int S44 = 21;
    static final byte[] PADDING = {-128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0};
    /**//*
     * 下面的三个成员是keyBean计算过程中用到的3个核心数据，在原始的C实现中 被定义到keyBean_CTX结构中
     * 
     */

    private long[] state = new long[4]; // state (ABCD)

    private long[] count = new long[2]; // number of bits, modulo 2^64 (lsb
    // first)

    private byte[] buffer = new byte[64]; // input buffer

    /**//*
     * digestHexStr是keyBean的唯一一个公共成员，是最新一次计算结果的 16进制ASCII表示.
     */
    public String digestHexStr;

    /**//*
     * digest,是最新一次计算结果的2进制内部表示，表示128bit的keyBean值.
     */
    private byte[] digest = new byte[16];

    /**//*
     * getkeyBeanofStr是类keyBean最主要的公共方法，入口参数是你想要进行keyBean变换的字符串
     * 返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．
     */

    public String getkeyBeanofStr(String inbuf) {
        keyBeanInit();
        keyBeanUpdate(inbuf.getBytes(), inbuf.length());
        keyBeanFinal();
        digestHexStr = "";
        for (int i = 0; i < 16; i++) {
            digestHexStr += byteHEX(digest[i]);
        }
        return digestHexStr;

    }

    // 这是keyBean这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
    public MD5() {
        keyBeanInit();
        return;
    }

    /**//* keyBeanInit是一个初始化函数，初始化核心变量，装入标准的幻数 */

    private void keyBeanInit() {
        count[0] = 0L;
        count[1] = 0L;
        // /* Load magic initialization constants.
        state[0] = 0x67452301L;
        state[1] = 0xefcdab89L;
        state[2] = 0x98badcfeL;
        state[3] = 0x10325476L;

        return;
    }

    /**//*
     * F, G, H ,I 是4个基本的keyBean函数，在原始的keyBean的C实现中，由于它们是
     * 简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们 实现成了private方法，名字保持了原来C中的。
     */

    private long F(long x, long y, long z) {
        return (x & y) | ((~x) & z);

    }

    private long G(long x, long y, long z) {
        return (x & z) | (y & (~z));

    }

    private long H(long x, long y, long z) {
        return x ^ y ^ z;
    }

    private long I(long x, long y, long z) {
        return y ^ (x | (~z));
    }

    /**//*
     * FF,GG,HH和II将调用F,G,H,I进行近一步变换 FF, GG, HH, and II transformations for
     * rounds 1, 2, 3, and 4. Rotation is separate from addition to prevent
     * recomputation.
     */

    private long FF(long a, long b, long c, long d, long x, long s, long ac) {
        a += F(b, c, d) + x + ac;
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;
        return a;
    }

    private long GG(long a, long b, long c, long d, long x, long s, long ac) {
        a += G(b, c, d) + x + ac;
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;
        return a;
    }

    private long HH(long a, long b, long c, long d, long x, long s, long ac) {
        a += H(b, c, d) + x + ac;
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;
        return a;
    }

    private long II(long a, long b, long c, long d, long x, long s, long ac) {
        a += I(b, c, d) + x + ac;
        a = ((int) a << s) | ((int) a >>> (32 - s));
        a += b;
        return a;
    }

    /**//*
     * keyBeanUpdate是keyBean的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个
     * 函数由getkeyBeanofStr调用，调用之前需要调用keyBeaninit，因此把它设计成private的
     */

    private void keyBeanUpdate(byte[] inbuf, int inputLen) {

        int i, index, partLen;
        byte[] block = new byte[64];
        index = (int) (count[0] >>> 3) & 0x3F;
        // /* Update number of bits */
        if ((count[0] += (inputLen << 3)) < (inputLen << 3)) {
            count[1]++;
        }
        count[1] += (inputLen >>> 29);

        partLen = 64 - index;

        // Transform as many times as possible.
        if (inputLen >= partLen) {
            keyBeanMemcpy(buffer, inbuf, index, 0, partLen);
            keyBeanTransform(buffer);

            for (i = partLen; i + 63 < inputLen; i += 64) {

                keyBeanMemcpy(block, inbuf, 0, i, 64);
                keyBeanTransform(block);
            }
            index = 0;

        } else {
            i = 0;
        }

        // /* Buffer remaining input */
        keyBeanMemcpy(buffer, inbuf, index, i, inputLen - i);

    }

    /**//*
     * keyBeanFinal整理和填写输出结果
     */

    private void keyBeanFinal() {
        byte[] bits = new byte[8];
        int index, padLen;

        // /* Save number of bits */
        Encode(bits, count, 8);

        // /* Pad out to 56 mod 64.
        index = (int) (count[0] >>> 3) & 0x3f;
        padLen = (index < 56) ? (56 - index) : (120 - index);
        keyBeanUpdate(PADDING, padLen);

        // /* Append length (before padding) */
        keyBeanUpdate(bits, 8);

        // /* Store state in digest */
        Encode(digest, state, 16);

    }

    /**//*
     * keyBeanMemcpy是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的
     * 字节拷贝到output的outpos位置开始
     */

    private void keyBeanMemcpy(byte[] output, byte[] input, int outpos,
            int inpos, int len) {
        int i;

        for (i = 0; i < len; i++) {
            output[outpos + i] = input[inpos + i];
        }
    }

    /**//*
     * keyBeanTransform是keyBean核心变换程序，有keyBeanUpdate调用，block是分块的原始字节
     */

    private void keyBeanTransform(byte block[]) {
        long a = state[0], b = state[1], c = state[2], d = state[3];
        long[] x = new long[16];
        Decode(x, block, 64);
        /**//* Round 1 */

        a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /**//* 1 */


        d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /**//* 2 */


        c = FF(c, d, a, b, x[2], S13, 0x242070dbL); /**//* 3 */


        b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /**//* 4 */


        a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /**//* 5 */


        d = FF(d, a, b, c, x[5], S12, 0x4787c62aL); /**//* 6 */


        c = FF(c, d, a, b, x[6], S13, 0xa8304613L); /**//* 7 */


        b = FF(b, c, d, a, x[7], S14, 0xfd469501L); /**//* 8 */


        a = FF(a, b, c, d, x[8], S11, 0x698098d8L); /**//* 9 */


        d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /**//* 10 */


        c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /**//* 11 */


        b = FF(b, c, d, a, x[11], S14, 0x895cd7beL); /**//* 12 */


        a = FF(a, b, c, d, x[12], S11, 0x6b901122L); /**//* 13 */


        d = FF(d, a, b, c, x[13], S12, 0xfd987193L); /**//* 14 */


        c = FF(c, d, a, b, x[14], S13, 0xa679438eL); /**//* 15 */


        b = FF(b, c, d, a, x[15], S14, 0x49b40821L); /**//* 16 */
        /**//* Round 2 */



        a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /**//* 17 */


        d = GG(d, a, b, c, x[6], S22, 0xc040b340L); /**//* 18 */


        c = GG(c, d, a, b, x[11], S23, 0x265e5a51L); /**//* 19 */


        b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /**//* 20 */


        a = GG(a, b, c, d, x[5], S21, 0xd62f105dL); /**//* 21 */


        d = GG(d, a, b, c, x[10], S22, 0x2441453L); /**//* 22 */


        c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /**//* 23 */


        b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /**//* 24 */


        a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /**//* 25 */


        d = GG(d, a, b, c, x[14], S22, 0xc33707d6L); /**//* 26 */


        c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /**//* 27 */


        b = GG(b, c, d, a, x[8], S24, 0x455a14edL); /**//* 28 */


        a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /**//* 29 */


        d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /**//* 30 */


        c = GG(c, d, a, b, x[7], S23, 0x676f02d9L); /**//* 31 */


        b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /**//* 32 */

        /**//* Round 3 */


        a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /**//* 33 */


        d = HH(d, a, b, c, x[8], S32, 0x8771f681L); /**//* 34 */


        c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /**//* 35 */


        b = HH(b, c, d, a, x[14], S34, 0xfde5380cL); /**//* 36 */


        a = HH(a, b, c, d, x[1], S31, 0xa4beea44L); /**//* 37 */


        d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /**//* 38 */


        c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /**//* 39 */


        b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /**//* 40 */


        a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /**//* 41 */


        d = HH(d, a, b, c, x[0], S32, 0xeaa127faL); /**//* 42 */


        c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /**//* 43 */


        b = HH(b, c, d, a, x[6], S34, 0x4881d05L); /**//* 44 */


        a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /**//* 45 */


        d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /**//* 46 */


        c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /**//* 47 */


        b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /**//* 48 */
        /**//* Round 4 */



        a = II(a, b, c, d, x[0], S41, 0xf4292244L); /**//* 49 */


        d = II(d, a, b, c, x[7], S42, 0x432aff97L); /**//* 50 */


        c = II(c, d, a, b, x[14], S43, 0xab9423a7L); /**//* 51 */


        b = II(b, c, d, a, x[5], S44, 0xfc93a039L); /**//* 52 */


        a = II(a, b, c, d, x[12], S41, 0x655b59c3L); /**//* 53 */


        d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /**//* 54 */


        c = II(c, d, a, b, x[10], S43, 0xffeff47dL); /**//* 55 */


        b = II(b, c, d, a, x[1], S44, 0x85845dd1L); /**//* 56 */


        a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /**//* 57 */


        d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /**//* 58 */


        c = II(c, d, a, b, x[6], S43, 0xa3014314L); /**//* 59 */


        b = II(b, c, d, a, x[13], S44, 0x4e0811a1L); /**//* 60 */


        a = II(a, b, c, d, x[4], S41, 0xf7537e82L); /**//* 61 */


        d = II(d, a, b, c, x[11], S42, 0xbd3af235L); /**//* 62 */


        c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /**//* 63 */


        b = II(b, c, d, a, x[9], S44, 0xeb86d391L); /**//* 64 */


        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;

    }

    /**//*
     * Encode把long数组按顺序拆成byte数组，因为java的long类型是64bit的， 只拆低32bit，以适应原始C实现的用途
     */

    private void Encode(byte[] output, long[] input, int len) {
        int i, j;

        for (i = 0, j = 0; j < len; i++, j += 4) {
            output[j] = (byte) (input[i] & 0xffL);
            output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);
            output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);
            output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);
        }
    }

    /**//*
     * Decode把byte数组按顺序合成成long数组，因为java的long类型是64bit的，
     * 只合成低32bit，高32bit清零，以适应原始C实现的用途
     */

    private void Decode(long[] output, byte[] input, int len) {
        int i, j;

        for (i = 0, j = 0; j < len; i++, j += 4) {
            output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8)
                    | (b2iu(input[j + 2]) << 16) | (b2iu(input[j + 3]) << 24);
        }

        return;
    }

    /**//*
     * b2iu是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
     */

    public static long b2iu(byte b) {
        return b < 0 ? b & 0x7F + 128 : b;
    }

    /**//*byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示，
     因为java中的byte的toString无法实现这一点，我们又没有C语言中的
     sprintf(outbuf,"％02X",ib)
     */

    public static String byteHEX(byte ib) {
        char[] Digit = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',
            'B', 'C', 'D', 'E', 'F'};
        char[] ob = new char[2];
        ob[0] = Digit[(ib >>> 4) & 0X0F];
        ob[1] = Digit[ib & 0X0F];
        String s = new String(ob);
        return s;
    }
}
